I am a quasar aficionado. Unfortunately the more quasar papers I read the more questions I have. There are puzzles within enigmas.

If any one is interested in this subject I would highly recommend Schneider's Extraglactic Astronomy & Cosmology. Schneider is a professional astronomer. His book is unusual as it explains what is observed, what is the standard theory that explains what is observed at an equation level, and then he includes a few sentences that explain problems with the current theory. Schneider has a deep understand of his subject as is shown in his mathematical explanation. He explains and constructs the mathematical models in a manner that is clear without losing the fact that this is an observational field.

Answering the question what the heck are quasars is one of the most important unanswered questions in astronomy. As more is known about this subject the explanations become increasingly rococo.

One of the questions that Schneider asks is why is there very, very, hot extra galactic gas between galactic clusters. He shows with equations that the gas should have had an opportunity to cool yet it has not. In addition the very very hot intergalactic gas is connected in massive intergalactic filaments.

We consider the impact of quasar outflows on structure formation. Such outflows are potentially more important than galactic winds, which appear insufficient to produce the level of preheating inferred from X-ray observations of galaxy clusters. Using a simple analytical model for the distribution of quasars with redshift, coupled with a one-dimensional Sedov-Taylor model for outflows, we are able to make robust statements about their impact of on structure formation. As large regions of the IGM are heated above a critical entropy of approximately 100 keV cm^2, cooling become impossible within them, regardless of changes in density. On quasar scales, this has the effect of inhibiting further formation, resulting in the observed fall-off in their number densities below z = 2. On galaxy scales, quasar feedback fixes the turn-over scale in the galaxy luminosity function (L_*) as the nonlinear scale at the redshift of strong feedback. The galaxy luminosity function then remains largely fixed after this epoch, consistent with recent observations and in contrast to the strong evolution predicted in more standard galaxy-formation models. Finally, strong quasar feedback explains why the intracluster medium is observed to have been pre-heated to entropy levels just above S_crit, the minimum excess that would not have been erased by cooling. The presence of such outflows is completely consistent with the observed properties of the Lyman-alpha forest at z ~ 2, but is expected to have a substantial and detectable impact on Compton distortions observed in the microwave background and the multiphase properties of the "warm-hot" (z=0) circumgalactic medium.